The principal objective of the project is to describe the microcircuitry of the cortex and to determine the functional role of each element of the cortical circuit. To do this we intend to employ a number of techniques. One is to record from cortical cells intracellularly and to inject them with a marker capable of labeling their entire dendritic and axonal trees. This provides insight into the pathways through which information is processed in the cortex. A second technique involves recording from an in vitro brain slice preparation, which should help elucidate the nature of the synaptic interaction between cells in the cortex, and which will help identify the chemical transmitters used by cortical cells. As an adjunct to these studies, we will do pharmacological experiments to further elaborate the role of individual connections. By contributing to an understanding of the basic mechanisms by which the cortex processes information, we hope to provide a basis for understanding the pathophysiology of various dysfunctional states that involve the cortex.